This invention relates to a method of preparing leaf protein, especially a method of preparing leaf protein with Hybrid Rumex Acetosa L. and the product prepared thereby
The grass forage is insufficient, especially those kinds of forage containing high protein level. It is a significant obstacle in respect of developing livestock industry. In the past, all of us considered alfalfa as a high yield species. However, we found that the amount of protein in alfalfa cannot meet our requirements.
Hybrid Rumex Acetosa L. is a new plant species, examined and certified by State Committee for Examination and Determination of Grass Species. It was issued a certificate of new grass species under Registration No. 183. Hybrid Rumex Acetosa L. belongs to Knotweed Acetosa, and is a perennial herbaceous herb. Its female parent is Rumex patienia L., and the male one is Rumex tianschanica L. 
Hybrid Rumex Acetosa L. is a high yield, high protein, green juicy forage crop. The protein content is high. The crude protein at the stage of leaves is as high as 30-34%, and 28-29% at the stage of buds. It can not only promote development of farming of cows and pigs, poultry and fishery, but it can also promote and push forward industralization of livestock industry and development of economy. That is because people have in mind the situation, that supply of leaf protein, grass powder and pellets cannot meet demands both in domestic and international markets, aid they will carry on the development of in-depth processing of Hybrid Rumex Acetosa L. 
During the first year, Hybrid Rumex Acetosa L. does not put forth stemming, and is under a condition of just having leaves. Thus, at this stage, the nutrition value of the forage grass is very high: the content of crude protein is 30-34%. In the second year, it puts forth stemming, blossoms and bears fruits. Usually, it is cut at the stage of budding. The regenerative grass is also cut at the stage of budding; at this period of time the content of crude protein is 27.07-29.94%. The yield is high, too: the yield of Hybrid Rumex Acetosa L. is 1300 kg dry grass/0.0667 hectare, and the crude protein represents 28%, while those of violet alfalfa are 1000 kg /0.0667 hectare and 18% only. That is, we have 364 kg of protein/0.0667 hectare for Hybrid Rumex Acetosa L., which is 2.02 times 180 kg for violet alfalfa.
The livestock industry cannot exist without high protein forage, while mankind requires high protein food and drinks, too. At present, additives either in our food or in our drinks have properties of chemical synthesis, and even more, some of them contain properties of gene synthesis. Along with improvements of people""s living and nutritious standards, green products, having highly nutritious ingredients of high protein, vitamins and carotene, for sure will be liked by massive people.
Therefore, an object of this invention is to provide a method for preparing leaf protein with Hybrid Rumex Acetosa L. 
Another object of this invention is to provide the product prepared by the method.
In order to achieve the above-mentioned objects, according to the application there is provided a method for preparing leaf protein, wherein Hybrid Rumex Acetosa L. is washed and squeezed, the obtained juice is heated to 70-90xc2x0 C., and cotton-like protein precipitate occurs. Supernatants arc removed, and paste-like Hybrid Rumex Acetosa L. leaf protein product is obtained.
The process of heating the juice as mentioned above can be replaced by adding acid into the squeezed juice. That is, cotton-like protein precipitate can also be obtained by adding acid into the squeezed juice. After supernatants are removed, paste-like Hybrid Rumex Acetosa L. protein product is obtained. The said acid can be citric acid or fruit acid.
The production method of this invention can further comprise the steps of preparing Rumex leaf protein in form of pellets or powder by drying the paste-like Rumex leaf protein.
The Rumex supernatants can be used to soak straws of agricultural crops, effectively increasing nutritious ingredients of straws, and improving palatability for animals as a new resource of new forage.
The method of this invention can further comprise the steps of preparing grass powder, grass pellets and grass bricks by drying, crushing, or pressing the byproduct, obtained as straw residue after squeezing the Hybrid Rumex Acetosa L. leaves.
It can be known that, the above mentioned leaf protein, which is a protein extracted from an entire plant, is called plant protein. It does not contain any oil substances, so it is a substitute of animal forage.
Leaf protein, obtained from Hybrid Rumex AceTosa L., is a highly value-added protein forage. According to information available, insufficient supply of protein forage is a common issue worldwide, and it is especially prominent in China, It is reported that the production of protein forage will be 2000 tons less than what is demanded in 2000. Especially in China, the production of grass powder is still at its beginning stage The production of green forage is 100 million tons less than what is demanded in China, while South Korea, Japan, Singapore, Hong Kong, Taiwan and other countries and regions all import green forage (grass powder, grass bricks, grass pellets) more than 300 tons every year. Therefore, it makes significant economic and social sense to produce green forage rich in protein, and to produce its byproducts (grass powder and grass pellets) with Hybrid Rumex Acetosa L. 
In addition, the leaf protein, obtained from Hybrid Rumex Acetosa L., can not only be used as highly value-added protein forage, but also as a nutritious and health-care product for mankind to improve diet structure of Chinese people.
The leaf protein, obtained from Hybrid Rumex Acetosa L., contains various amino acids, and the kinds of amino acids are rather complete. If amino acids for synthesizing protein are not enough in human body, the content of protein in blood will be low, resulting in anaemia. Hybrid Rumex Acetosa L. provides the human body with relatively balanced amino acids (see table 2), especially it contains much lysine, which can supplement insufficient provision of amino acids just with cereal products
The leaf protein, obtained from Hybrid Rumex Acetosa L., also contains a variety of vitamins and lutein, as well as other nutritious elements like iron, magnesium, calcium, zinc, etc. There is no cholesterol like that contained in animal food. (See table 3). It can be used to improve people""s diet structure. At present, there have been many specialists in the field of nutrition and food considering that the plant protein should be listed as an important source of nutrition.
The leaf protein, obtained from Hybrid Rumex Acetosa L., also contains a lot of organo-selenium. Organo-selenium is praised by medical circle worldwide as xe2x80x9cLife element of 21st centuryxe2x80x9d, because it has excellent effect in preventing cancer. Even more is that there are very few organo-selenium resources, from which the human body can absorb selenium directly, so it is said the element is more precious than gold and diamond.
According to the application, the method for preparing leaf protein with Hybrid Rumex Acetosa L. is scientific and reasonable, simple, easy to implement. The obtained product has a color of dark green with fragrant smell. There are no fermenting, moulding, and no bad odor. It can be use as highly value-added protein forage to solve the problem that China seriously lacks protein forage. It can also be used as purely natural green food. It can significantly improve the level of haemochrome in human body, and increase iron, calcium, and magnesium contents in blood. Symptoms of lack of nutrition can be eliminated. Long term drinking or eating food supplemented with leaf protein have good effect for pregnant women, old people, patients of anaemia, especially for kids"" development and health.